1. Field of the Invention
The present invention generally relates to tape drives and recording head actuator designs and, more particularly, to a recording head actuator assembly (and a tape drive incorporating such an assembly) adapted to address angular error or misalignment between read and write elements of a recording head and magnetic tape passing over the recording head.
2. Relevant Background
Tape drives have been widely employed in the data storage industry for over thirty years due to their ability to store large amounts of data on a relatively small and inexpensive removable format. Typically, tape drives use a storage tape that is wound between a pair of tape reels as data is transferred to or from the tape media via a read/write tape head assembly (or recording head actuator assembly). In one arrangement, one of the reels (e.g., the “take-up” reel) is part of the tape drive while the other reel (e.g., the “cartridge” or “supply” reel) is part of a removable cartridge. Upon insertion of the cartridge into the tape drive, the storage tape on the cartridge reel is coupled to the take-up reel of the tape drive (e.g., via respective leaders). After coupling, the tape is unwound from the cartridge reel, moved past the recording head assembly and wound onto the take-up reel via a drive motor. Next, the tape is unwound from the take-up reel, moved past the tape head assembly and wound onto the cartridge. Subsequently, the storage tape must be uncoupled from the take-up reel, prior to removing the cartridge from the tape drive. In another arrangement, both reels are part of a cassette which is inserted into a tape drive and driven by a drive motor.
To increase the storage density and reduce the access time of magnetic tapes, a popular trend is towards multi-head, multi-channel fixed head structures with narrowed recording gaps and data track widths so that many linear data tracks may be manipulated on a tape medium of a predetermined width (e.g., such as one-half inch width tape) passing by the head structures at increasingly faster rates of speed. However, various factors work against the ability of present systems to achieve such increased storage densities and reduced access times.
Physically storing data on magnetic tape remains crucial in the data storage industry, but this will only continue as long as the data stored on the tape remains uncorrupted, resists degradation over large spans of time, and can readily be retrieved from the tape. One problem presently plaguing the date storage industry is related to the dimensional stability of the magnetic tape. More specifically, the resolution of the tracks on the tape have become so fine that variations in temperature, humidity, and pressure can change the physical dimensions between the tracks on the tape (also called tape dimensional stability (TDS)), but, at the same time, similar changes do not occur within the recording head such that the spacing of the read and write elements remain unchanged. As a result, there can be track misregistration (TMR), e.g., between servo tracks and servo readers and between read elements and written tracks, due to TDS that can cause errors in later reading data from the tape and writing new data to the tape.
TMR can also result from an angular misalignment between the recording head and the tape (e.g., the tape is at an angle (often labeled as an azimuth angle) relative to the read and write elements instead of running perfectly orthogonal to the head). At this point, it may be useful to further discuss tape motion and its variation to understand the problem of TMR in a typical tape drive. Lateral tape motion (LTM) refers to the vertical motion of the tape in reference to the recording head. This motion can become problematic when the fine tracks of the tape become offset in regards to the writing portion of the recording head. This issue has been accounted for by use of two motors (a coarse motor along with a fine motor) actuating the recording head assembly to trace the lateral tape motion or motion of the servo tracks on the tape. In contrast with regard to angular misalignment, an azimuth in mathematics is simply an angular measurement in spherical coordinates, and azimuth (sometimes referred to as skew) in a tape drive can be caused by the non-linear motion of the tape relative to the recording head. In the tape drive, an error can be caused due to the existence of a non-zero azimuth angle between the recording head (i.e., a line extending through the linearly arranged read and write elements on the head) and a line extending perpendicular to the direction of travel for the tape.
Hence, there remains a need for a recording head assembly that is better designed to address TMR and to reduce the likelihood of errors caused by TDS or by the tape being at an unexpected azimuth angle relative to the recording head. Preferably, the new recording head assembly would be useful in existing tape drive configurations, e.g., the size of the assembly would fit within space presently provided for a recording head assembly, and, further, it would be useful for the assembly to be relatively inexpensive to manufacture while having an acceptably long service life.